Study On The Preparation And Performance Of PVA/PAA-based Supramolecular Hydrogel

Supramolecular hydrogels are hydrogels formed with non-covalent bonds used as cross-linking points.Non-covalent bonds provide energy dissipation mechanism as reversible "sacrificial"bonds in the hydrogel network structure.Conventional hydrogels prepared by one physical cross-linking method have poor mechanical properties,however,the strength and toughness of the hydrogels can be significantly increased by the synergistic effect of two or more non-covalent bonds.Furthermore,in orderto extend the electriciticy of hydrogels,combining conductive polymers with hydrogels imparts hydrogel conductive propertity.In this study,fistly,the hydrogen bonding interaction sites of polymer some molecules were simulated by using quantum chemical calculation method.Secondly,high mechanical PVA/PAA/FerC hydrogels and conductive PVA/PAA/PANI hydrogels were prepared by using non-covalent bonds,such as coordination bonds and hydrogen bonds,as physical crosslinks,which were simple and versatilemethods.The detail contents are as follows:PVA/PAA supramolecular hydrogels were prepared by using biocompatible polyvinyl alcohol(PVA)and acrylic acid(AA)as raw materials,based on hydrogen bonding as physical crosslinking points,and then PVA/PAA/Fe3+ hydrogels have been prepared by PVA/PAA hydrogels according to coordination bonds.The effects of hydrochloric acid concentration,Fere concentration and soaking time on the mechanical properties of supermolecular hydrogels were investigated,respectively.The stability of the hydrogel was investigated by the pH value of the solution.The self-recovery of hydrogel was evaluated by cyclic loading-unloading experiment.FTIR results showed that the formation of hydrogen bonds as well as coordination bonds.The hydrogel possessed the best mechanical strength with the tensile stress at break of 12.69 MPa and toughness of 41.64 MJ/m3 under the conditions of 0.2 mol/L hydrochloric acid,0.09 mol/L Fe3+ and 20 h soaking time.The hydrogel is stable when the pH value is 1-9.After a cyclic loading-unloading experiment and waiting for 240 minutes,the stress and strain recovery rates of hydrogels can reach 90%and 87.80%,respectively.The shape memory function is realized by the reversible exchange between the hydrogel and H+ in the external environment.Based on the PVA/PAA supramolecular hydrogel,PVA/PAA/PANI conductive hydrogels with uniform structure distribution was prepared by mixing PVA,AA and aniline(ANI)by the "one-pot,two-steps" method with hydrogen bonding as physical crosslinking point.The mechanical and conductive properties of the hydrogel were investigated by adjusting the content of aniline,and the fatigue resistance of the hydrogel was evaluated by cyclic loading-unloading experiments.The results showed that when the content of aniline was 10 wt%,the best break strength was as high as 0.49 MPa,and the compressive strength was 2.7 MPa with 80%deformation change.And when the aniline content was 16.6 wt%,the hydrogel had the best conductivity,about 4 S/m.In addition,after being subjected to 100%deformation cyclic loading-unloading,the hydrogel could be quickly recovered,and under the 300%deformation cyclic loading-unloading,the hydrogel had a transient unrecoverable property under large deformation.